The purpose of this study is to clarify the significance of allergen exposure in relation to the recent pollinosis outbreak. The results obtained were as follows :1. By an epidemiological study on the school children and their families, it was proven that prevalence of the pollinosis in the generation of parents and in the generation of children was significantly higher than that of the generation of grandparents. This study suggests that the generations of parents and children were exposed to the environmental factor that did not exist for the generation of grandparents.2. Though it was shown that the Japanese cedar pollen is the most important allergen in many regions, important roles of Gramineae pollen and pear pollen were also recognized in several regions. In Japanese cedar pollen exposure, both weather condition and the physiology fluctuation of the cedar were demonstrated to be important factors by atmospheric pollen survey.3. On the major allergen of Japanese cedar pollen, methodological investigation was performed. Cry j 1 in the pollen grain was evaluated quantitatively by an ELISA method. The method revealed to be a useful method for evaluation of the environmental allergen standard, which is acceptable for pollinosis patients.